By Jonathan Head
BBC News, Bangkok
Not much can bring the life of the noisy, traffic-clogged heart of Bangkok to a halt.
Thais say the king exhibits perfect Buddhist qualities
But on Wednesday the streets were hushed, the cars and buses banished.
All you could hear were speakers playing the royal anthem, and thousands of flags fluttering in the breeze, held by people of all ages.
Most were dressed in yellow and had waited for hours for a glimpse of a stiff and stern-faced old man passing in a motorcade, on his way to the gilded halls and temples of Bangkok's Grand Palace.
And as it passed they shouted "Song Phra Charoen", "Long Live Your Majesty". Some had tears in their eyes.
What explains this extraordinary bond between people and monarch?
King Bhumibol Adulyadej is accorded an almost divine reverence, with titles like Phra Chao Yu Hua (Lord Upon our Heads) or Chao Chiwit (Lord of Life).
People prostrate themselves on the ground in his presence. Yet there is genuine affection too, and it goes both ways.
Thais talk of their love for him as though he were a cherished member of the family.
In his speeches to the nation he likes to joke and tease them.
Pink clothing sales rocketed when the king left hospital in a pink suit
Earlier in his reign when he was younger and travelled a lot, he clearly enjoyed meeting and mixing with people from the poorest rural communities.
People often refer to his long life of service to the nation, to his experiments with agriculture and irrigation, many of them carried out on the grounds of his palace in Bangkok.
The formidable public relations machine which manages the monarchy's image makes much of these experiments, as it does of the king's other talents as a jazz musician and sailor.
But the real measure of these achievements is impossible to know in a country where all criticism of the monarchy is curtailed by the draconian lese majeste law (offence against the dignity of the monarch), and only lavish praise for the royal family can be published.
The reverence for the king seems rooted in something less worldly.
Time after time when Thais are asked about the virtues of King Bhumibol they refer to his proper adherence to the principles of "Dhamma", Buddhist teachings and the Buddhist concept of righteousness.
It is not just his practical deeds they are looking at, but his manner, his modesty, his reserve, his gentleness, and his apparent detachment from the world - qualities he has worked hard to perfect and project.
He is as much a spiritual leader as a worldly one.
During his six decades on the throne Thailand has undergone changes as wrenching as in any other country.
Per capita income has gone up 40-fold. An almost entirely agrarian society has become a substantially urban one. The economy has been swept along by the forces of globalisation.
There have been other changes as well.
The king's endorsement of the coup was essential to its success
This king has reigned through 17 military coups and 26 prime ministers. The gap between rich and poor has widened, with conspicuous consumption and conspicuous corruption accepted as part of everyday life.
There has been a corresponding decline in traditional community and family values.
Amid this whirlwind, the king has remained a reassuring anchor, a man who embodies Thailand's history but who has also come to embody integrity and detachment from the squalid realities of day-to-day politics and business.
He has lived the myth of the virtuous monarch so well that almost the entire population believes in it and takes comfort from it.
And it gives him a unique moral authority. When he speaks, people listen.
They may, and often do, fail to act on his advice. But he has been able to use that authority to settle a number of political crises.
"If the country were in good shape politically, then the role of the constitutional monarch is not very difficult," explains Suchit Bunbongkarn, professor of political science at Chulalongkorn University.
"But in the case of Thailand it is not easy because our political system has been unstable all the time. So whenever there is a political crisis people expect the king to solve the problem."
Former Prime Minister Anand Panyarachun describes King Bhumibol's authority as "reserve power" that, because it has been used judiciously and sparingly, has been decisive in maintaining the country's stability.
This power, he says, has been accumulated through a life of dedication to his job. It cannot, he points out, be inherited or passed on.
Fears and superstition
There is quiet concern about the abilities of the heir to the throne
That explains the acute anxiety now over the king's fragile health. Few imagine that any future monarch can match this one.
There are many reservations about the capabilities of his presumed heir, Crown Prince Vajiralongkorn, although these cannot be expressed publicly because of the lese majeste laws.
The succession itself is not completely clear, with the constitution leaving considerable powers to designate an heir to the 19-member Privy Council of senior advisors to the king.
The opacity that has preserved the mystique of monarchy in Thailand makes it impossible to discuss, let alone plan for the succession.
So Thais prefer not to think about it.
When I saw his tailor, Sompop Louilarpprasert, and asked him about the king's recent spell in hospital, he brushed it aside.
"I want to be making suits for him when he is 90 years old, when he is 100 - longer even."
It was Sompop who made the dazzling pink blazer the king wore when he came out of hospital.
Within hours, pink shirts were being sold in their thousands across the country, and there are days when some streets are a sea of pink.
In this superstitious country they now associate pink with the king's recovery. It will bring him good fortune, they say.
By wearing it they are literally willing him to stay alive for them.